Coating for and method of scale formation control on slabs and the like



Patented June 12, 1945 COATING FOR AND METHOD OF SCALE FORMATION CONTROL ON SLABS AND THE LIKE Albert N. Swanson, .Gary, Ind., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey No Drawing. Application February 19, 1943,

' Serial No. 476,494

4 Claims.

This invention relates to the heating of metallic articles, such as slabs, blooms, plates, sheets, bars and the like and, particularly, to an improved coating material for and method of; controllin the formation of scale thereon during the heating thereof so as toprevent detrimental scaling of such articles, especially alloy steel slabs.

It is conventional practice in the steel industry in the manufacture of alloy steel plates to first there is formed thereon what is known to those In ordinary carbon steel,

in the trade as scale. this scale is brittle and easily removed from the slabs during the rolling, thereof by means of steam, water or by brushing or scraping it; but on alloy steel slabs, particularly nickel alloys, this venting detrimental scaling of alloy steel slabs and the like which is simple and inexpensive at the same time, efficient and effective in its use.

Various other objects and advantages of my invention will become more apparent during the course of the following specification and claims. After the alloy steel ingots have been rolled into slabs and are ready for reheating for further rolling into plates and the like, the slabs are placed in a conventional reheating furnace having an oxidizing atmosphere, such as the reheating furnaces described above. According to the present invention, there is disposed on the top surface ofthe slabs which aresubject to the intense heat of the furnace, a relatively thin layer. 7

of pulverized ferro-phosphorus. Such a metallic alloy contains generally about 73 percent iron ill scale is extremely adherent to the slab surface and extremely difiicult to remove during rolling. Heretofore, it has been the practice generally to cover the alloy' steel slabs in the heating heating flames within the furnace, thus material:

1y reducing the scaling of this surface of the slabs. Such a means of protecting the surface of the slabs from scaling is unsatisfactory for the reason that it prolongs the time required to heat the slabs to the proper rolling temperature which results in an excessive amount of fuel being used thereby increasing the cost of heating of the slabs.

Accordingly, it is one of the objects of the present invention to provide an improved coating for alloy steel slabs and the like which reduces materially the time required for heating the slabs to a rolling temperature, thereby eliminating the above mentioned disadvantages.

It is another object of the invention to provide an improved coating for alloy steel slabs and the like which is characterized in that it makes the scale thereon loose and brittle thereby perm tting quick and convenient removal thereof by conventional methods, such as scraping or spraying.

It is a further object of this invention to pro vide an improved coating for and method of preand 23 percent phosphorus and is used in the steel industry'as an addition to the steel in the ladle when an additional phosphorus content is desired as in the case of tin plate. This player or coating of ferro-phosphorus is made to cover the entire top surface of the slabs and is preferably disposed thereon to a thickness of about A: of an inch. The slabs are then heated in the furnace with the coating of ferro-phosphorus disposed thereon until the desired temperature is reached, which is usually in the vicinity of 2300 to 2400 degrees Fahr.

It has been'found that during the heating of the slabs, the ferro-phosphorus combines with the normal alloy scale produced by the oxidizing atmosphere of the furnace in such a manner that the characteristics of the scale instead of bein tough and extremely adherent are relatively soft and brittle and a heavy loose friable scale is formed on the slabs. This scale can be easily and conveniently removed by conventional processes such as by scraping or spraying as in the case of scale on ordinary carbon steel slabs.

It will be understood that with the use of pulverized ferro-phosphorus as in the present invention, instead of using steel plate covers for protecting the top surface of alloy steel slabs from detrimental scaling, that the time required to reheat the slabs is reduced materially. For example, it has been found that a savings of eight hours is obtained in heating a slab nine inches thick bythe practice of my invention. It will also be understood that the phosphorus enrichment is confined to the scale and outer sides of the slabs and that it has no detrimental effect upon the quality of the rolled finished product or plate.

As a result of my invention, it will be seen that there is provided an improved coating for protecting the surface of alloy steel slabs from detrimental scaling which can be easily and quickly applied to the surface of the slabs, and there is formed on the slab after heating thereof a scale which can be easily and conveniently removed. It will also be seen that by the practice of the method of the present invention, that not only fuel and heat are saved but that a better finished product is obtained than by methods heretofore suggested and used.

From the above description of my invention, it will be apparent that many modifications of the same may be desired within the scope thereof and all such modifications are contemplated as may fall within the scope of the appended claims.

I claim:

1. In the manufacture of alloy steel articles the method which includes the steps of providing an alloy steel workpiece, disposing such workpiece in a furnace, placing a layer of pulverized ferrophosphorus on the surface of the workpiece, heat ing the workpiece to a hot working temperature in an oxidizing atmosphere whereby a loose brittle scale is formed on the coated surface of the workpiece, removing such scal from the workpiece, and hot working the heated workpiece.

Z. In the manufacture of alloy steel articles the phosphorus on the upper surface of the workpiece exposed to the direct heat of the furnace heating means, heating the workpiece to a hot working temperature in an oxidizing atmosphere whereby a loose brittle scale is formed on the coated surface of the workpiece, removing such scale from the workpiece, and hot working the heated workpiece.

3. In the manufacture of articles of nickel bearing steel the method which includes the steps of providing a nickel bearing steel workpiece, disposing such workpiece in a furnace, placing a layer of pulverized ferro-phosphorus on the surface of the workpiece, heating the workpiece to a hot working temperature in an oxidizing atmosphere whereby a loose brittle scale is formed on the coated surface of the workpiece, removing method which includes the steps of providing an alloy steel workpiece, disposing such workpiece in a furnace, placing a layer of pulverized ferrosuch scale from the workpiece, and hot working the heated workpiece.

4. In the manufacture of nickel bearing steel alloy plates the method which includes the steps of providing a nickel bearing steel slab, disposing such slab in a furnace, placing a layer of pulverized ferro-phosphorus on the surface of the workpiece, heating the slab to a hot working temperature in an oxidizing atmosphere whereby a loose brittle scale is formed on the coated surface of the workpiece, removing such scale from the slab, and hot working the heated slab to reduce it to plate.

ALBERT N. SWANSON. 

